U.S. patent application number 14/145207 was filed with the patent office on 2014-07-03 for photoresist pattern trimming methods.
The applicant listed for this patent is Rohm and Haas Electronic Materials LLC. Invention is credited to Gerhard POHLERS, Kevin ROWELL, Cheng-Bai XU.
Application Number | 20140186772 14/145207 |
Document ID | / |
Family ID | 51017569 |
Filed Date | 2014-07-03 |
United States Patent
Application |
20140186772 |
Kind Code |
A1 |
POHLERS; Gerhard ; et
al. |
July 3, 2014 |
PHOTORESIST PATTERN TRIMMING METHODS
Abstract
Provided are methods of trimming a photoresist pattern. The
methods comprise: (a) providing a semiconductor substrate; (b)
forming a photoresist pattern on the substrate, wherein the
photoresist pattern is formed from a chemically amplified
photoresist composition comprising: a matrix polymer comprising an
acid labile group; a photoacid generator; and a solvent; (c)
coating a photoresist trimming composition on the substrate over
the photoresist pattern, wherein the trimming composition
comprises: a matrix polymer, an aromatic acid that is free of
fluorine; and a solvent; (d) heating the coated substrate, thereby
causing a change in polarity of the photoresist matrix polymer in a
surface region of the photoresist pattern; and (e) contacting the
photoresist pattern with a rinsing agent to remove the surface
region of the photoresist pattern, thereby forming a trimmed
photoresist pattern. The methods find particular applicability in
the manufacture of semiconductor devices.
Inventors: |
POHLERS; Gerhard; (Needham,
MA) ; XU; Cheng-Bai; (Southborough, MA) ;
ROWELL; Kevin; (Brighton, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Rohm and Haas Electronic Materials LLC |
Marlborough |
MA |
US |
|
|
Family ID: |
51017569 |
Appl. No.: |
14/145207 |
Filed: |
December 31, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61748035 |
Dec 31, 2012 |
|
|
|
Current U.S.
Class: |
430/311 |
Current CPC
Class: |
G03F 7/0397 20130101;
G03F 7/405 20130101 |
Class at
Publication: |
430/311 |
International
Class: |
G03F 7/40 20060101
G03F007/40 |
Claims
1. A method of trimming a photoresist pattern, comprising: (a)
providing a semiconductor substrate; (b) forming a photoresist
pattern on the substrate, wherein the photoresist pattern is formed
from a chemically amplified photoresist composition comprising: a
matrix polymer comprising an acid labile group; a photoacid
generator; and a solvent; (c) coating a photoresist trimming
composition on the substrate over the photoresist pattern, wherein
the trimming composition comprises: a matrix polymer, an aromatic
acid that is free of fluorine; and a solvent; (d) heating the
coated substrate, thereby causing a change in polarity of the
photoresist matrix polymer in a surface region of the photoresist
pattern; and (e) contacting the photoresist pattern with a rinsing
agent to remove the surface region of the photoresist pattern,
thereby forming a trimmed photoresist pattern.
2. The method of claim 1, wherein the aromatic acid comprises an
acid of the general formula (I): ##STR00012## wherein: R.sup.1
independently represents a substituted or unsubstituted C1-C20
alkyl group, a substituted or unsubstituted C5-C20 aryl group or a
combination thereof, optionally containing one or more group chosen
from carbonyl, carbonyloxy, sulfonamido, ether, thioether, a
substituted or unsubstituted alkylene group, or a combination
thereof; Z.sup.1 independently represents a group chosen from
carboxyl, hydroxy, nitro, cyano, C1 to C5 alkoxy, formyl and
sulfonic acid; a and b are independently an integer from 0 to 5;
and a+b is 5 or less.
3. The method of claim 1, wherein the aromatic acid comprises an
acid of the general formula (II): ##STR00013## wherein: R.sup.2 and
R.sup.3 each independently represents a substituted or
unsubstituted C1-C20 alkyl group, a substituted or unsubstituted
C5-C16 aryl group or a combination thereof, optionally containing
one or more group chosen from carbonyl, carbonyloxy, sulfonamido,
ether, thioether, a substituted or unsubstituted alkylene group, or
a combination thereof; Z.sup.2 and Z.sup.3 each independently
represents a group chosen from carboxyl, hydroxy, nitro, cyano, C1
to C5 alkoxy, formyl and sulfonic acid; c and d are independently
an integer from 0 to 4; c+d is 4 or less; e and f are independently
an integer from 0 to 3; and e+f is 3 or less.
4. The method of claim 1, wherein the aromatic acid comprises an
acid of the general formula (III) or (IV): ##STR00014## wherein:
R.sup.4, R.sup.5 and R.sup.6 each independently represents a
substituted or unsubstituted C1-C20 alkyl group, a substituted or
unsubstituted C5-C12 aryl group or a combination thereof,
optionally containing one or more group chosen from carbonyl,
carbonyloxy, sulfonamido, ether, thioether, a substituted or
unsubstituted alkylene group, or a combination thereof; Z.sup.4,
Z.sup.5 and Z.sup.6 each independently represents a group chosen
from carboxyl, hydroxy, nitro, cyano, C1 to C5 alkoxy, formyl and
sulfonic acid; g and h are independently an integer from 0 to 4;
g+h is 4 or less; i and j are independently an integer from 0 to 2;
i+j is 2 or less; k and l are independently an integer from 0 to 3;
and k+l is 3 or less; ##STR00015## wherein: R.sup.4, R.sup.5 and
R.sup.6 each independently represents a substituted or
unsubstituted C1-C20 alkyl group, a substituted or unsubstituted
C5-C12 aryl group or a combination thereof, optionally containing
one or more group chosen from carbonyl, carbonyloxy, sulfonamido,
ether, thioether, a substituted or unsubstituted alkylene group, or
a combination thereof; Z.sup.4, Z.sup.5 and Z.sup.6 each
independently represents a group chosen from carboxyl, hydroxy,
nitro, cyano, C1 to C5 alkoxy, formyl and sulfonic acid; g and h
are independently an integer from 0 to 4; g+h is 4 or less; i and j
are independently an integer from 0 to 1; i+j is 1 or less; k and l
are independently an integer from 0 to 4; and k+l is 4 or less.
5. The method of claim 1, wherein the aromatic acid comprises an
acid of the general formula (V): ##STR00016## wherein: R.sup.7 and
R.sup.8 each independently represents a substituted or
unsubstituted C1-C20 alkyl group, a substituted or unsubstituted
C5-C14 aryl group or a combination thereof, optionally containing
one or more group chosen from carboxyl, carbonyl, carbonyloxy,
sulfonamido, ether, thioether, a substituted or unsubstituted
alkylene group, or a combination thereof; Z.sup.7 and Z.sup.8 each
independently represents a group chosen from hydroxy, nitro, cyano,
C1 to C5 alkoxy, formyl and sulfonic acid; m and n are
independently an integer from 0 to 5; m+n is 5 or less; o and p are
independently an integer from 0 to 4; and o+p is 4 or less.
6. The method of claim 1, wherein the aromatic acid comprises an
acid of the general formula (VI): ##STR00017## wherein: X is O or
S; R.sup.9 independently represents a substituted or unsubstituted
C1-C20 alkyl group, a substituted or unsubstituted C5-C20 aryl
group or a combination thereof, optionally containing one or more
group chosen from carbonyl, carbonyloxy, sulfonamido, ether,
thioether, a substituted or unsubstituted alkylene group, or a
combination thereof; Z.sup.9 independently represents a group
chosen from carboxyl, hydroxy, nitro, cyano, C1 to C5 alkoxy,
formyl and sulfonic acid; q and r are independently an integer from
0 to 3; and q+r is 3 or less.
7. The method of claim 1, wherein the solvent of the trimming
composition comprises an organic solvent.
8. The method of claim 1, wherein the trimming composition is an
aqueous solution.
9. The method of claim 1, wherein the rinsing agent comprises water
or an aqueous alkaline solution.
10. The method of claim 1, wherein the rinsing agent comprises an
organic solvent or solvent mixture.
Description
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn.119(e) to U.S. Provisional Application No. 61/748,035,
filed Dec. 31, 2012, the entire contents of which application are
incorporated herein by reference.
BACKGROUND
[0002] The invention relates generally to the manufacture of
electronic devices. More specifically, this invention relates to
methods of trimming photoresist patterns useful in shrink processes
for the formation of fine lithographic patterns.
[0003] In the semiconductor manufacturing industry, photoresist
materials are used for transferring an image to one or more
underlying layers, such as metal, semiconductor and dielectric
layers, disposed on a semiconductor substrate, as well as to the
substrate itself. Photoresist materials further find use in
semiconductor manufacture in the formation of ion implantation
masks. To increase the integration density of semiconductor devices
and allow for the formation of structures having dimensions in the
nanometer range, photoresists and photolithography processing tools
having high-resolution capabilities have been and continue to be
developed.
[0004] Positive-tone chemically amplified photoresists are
conventionally used for high-resolution processing. Such resists
typically employ a resin having acid-labile leaving groups and a
photoacid generator. Exposure to actinic radiation causes the acid
generator to form an acid which, during post-exposure baking,
causes cleavage of the acid-labile groups in the resin. This
creates a difference in solubility characteristics between exposed
and unexposed regions of the resist in an aqueous alkaline
developer solution. In a positive tone development (PTD) process,
exposed regions of the resist are soluble in the aqueous alkaline
developer and are removed from the substrate surface, whereas
unexposed regions, which are insoluble in the developer, remain
after development to form a positive image.
[0005] One approach to achieving nm-scale feature sizes in
semiconductor devices is the use of short wavelengths of radiation
such as 200 nm or less, for example, 193 nm or EUV wavelengths
(e.g., 13.5 nm) during exposure of chemically amplified
photoresists. To further improve lithographic performance,
immersion lithography tools have been developed to effectively
increase the numerical aperture (NA) of the lens of the imaging
device, for example, a scanner having a KrF or ArF light source.
This is accomplished by use of a relatively high refractive index
fluid (i.e., an immersion fluid) between the last surface of the
imaging device and the upper surface of the semiconductor wafer.
The immersion fluid allows a greater amount of light to be focused
into the resist layer than would occur with an air or inert gas
medium. When using water as the immersion fluid, the maximum
numerical aperture can be increased, for example, from 1.2 to 1.35.
With such an increase in numerical aperture, it is possible to
achieve a 40 nm half-pitch resolution in a single exposure process,
thus allowing for improved design shrink. This standard immersion
lithography process, however, is generally not suitable for
manufacture of devices requiring greater resolution, for example,
for the 32 nm and 22 nm half-pitch nodes.
[0006] Considerable effort has been made to extend the practical
resolution beyond that achieved with standard photolithographic
techniques from both a materials and processing standpoint. For
example, multiple (i.e., double or higher order) patterning
processes have been proposed for printing CDs and pitches beyond
lower resolution limits of conventional lithographic tools. One
such double patterning process is litho-litho-etch (LLE) double
patterning, which involves formation of a first lithographic
photoresist pattern followed by formation of a second lithographic
photoresist pattern, wherein lines of the second pattern are
disposed between adjacent lines of the first pattern. Such a
process is disclosed, for example, in U.S. Patent Application
Publication No. US2008/0063985A1. LLE double patterning and other
advanced lithographic processes often require the formation of
isolated features such as lines or posts by direct lithographic
printing. The formation of isolated features with an acceptable
process window, however, can pose a challenge as a result of poor
aerial image contrast at defocus.
[0007] There is a continuing need in the art for improved
photolithographic methods for the formation of fine patterns in
electronic device fabrication.
SUMMARY OF THE INVENTION
[0008] In accordance with a first aspect of the invention, methods
of trimming a photoresist pattern are provided. The methods
comprise: (a) providing a semiconductor substrate; (b) forming a
photoresist pattern on the substrate, wherein the photoresist
pattern is formed from a chemically amplified photoresist
composition comprising: a matrix polymer comprising an acid labile
group; a photoacid generator; and a solvent; (c) coating a
photoresist trimming composition on the substrate over the
photoresist pattern, wherein the trimming composition comprises: a
matrix polymer, an aromatic acid that is free of fluorine; and a
solvent; (d) heating the coated substrate, thereby causing a change
in polarity of the photoresist matrix polymer in a surface region
of the photoresist pattern; and (e) contacting the photoresist
pattern with a rinsing agent to remove the surface region of the
photoresist pattern, thereby forming a trimmed photoresist
pattern.
[0009] In accordance with a further aspect of the invention,
provided are electronic devices formed by the methods described
herein.
[0010] Photoresist pattern trimming methods of the invention can
produce very fine lithographic patterns and process window for
formation of isolated patterns can be improved.
DESCRIPTION OF THE DRAWINGS
[0011] The present invention will be described with reference to
the following drawing, in which like reference numerals denote like
features, and in which:
[0012] FIG. 1A-I illustrates a process flow for forming a
photolithographic pattern in accordance with the invention.
DETAILED DESCRIPTION
Photoresist Trimming Compositions
[0013] The photoresist trimming compositions include a matrix
polymer, an aromatic acid that is free of fluorine and a solvent,
and can include optional additional components. When coated over a
photoresist pattern formed from a chemically amplified photoresist
composition, the photoresist trimming compositions can provide
various benefits such as controllably reduced resist pattern
dimensions and improved process window for the formation of
isolated patterns such as isolated lines and posts.
[0014] The matrix polymer allows for the compositions to be coated
over the photoresist pattern in the form of a layer having a
desired thickness. This will help to ensure the presence of a
sufficient content of acid for interaction with the photoresist
pattern surface.
[0015] The matrix polymer should have good solubility in the
developer solution to be used in the trimming process. For example,
the matrix polymer can be soluble in an aqueous alkaline developer,
preferably aqueous quaternary ammonium hydroxide solutions such as
aqueous tetramethylammonium hydroxide, or in water. To minimize
residue defects originated from the overcoat materials, the
dissolution rate of a dried layer of the trimming composition
should be greater than that of the photoresist pattern surface
region to be removed by the developer solution. The matrix polymer
typically exhibits a developer dissolution rate of 100 .ANG./second
or higher, preferably 1000 .ANG./second or higher. The matrix
polymer is soluble in the solvent of the trimming composition,
described herein. The matrix polymer can be chosen, for example,
from polyvinyl alcohols, polyacrylic acids, polyvinyl pyrrolidones,
polyvinyl amines, polyvinyl acetals, poly(meth)acrylates and
combinations thereof. Preferably, the polymer contains one or more
functional group chosen from --OH, --COOH, --SO.sub.3H, SiOH,
hydroxyl styrene, hydroxyl naphthalene, sulfonamide,
hexafluoroisopropyl alcohol, anhydrates, lactones, esters, ethers,
allylamine, pyrolidones and combinations thereof.
[0016] The content of the matrix polymer in the composition will
depend, for example, on the target thickness of the layer, with a
higher polymer content being used for thicker layers. The matrix
polymer is typically present in the compositions in an amount of
from 80 to 99 wt %, more typically from 90 to 98 wt %, based on
total solids of the trimming composition. The weight average
molecular weight of the polymer is typically less than 400,000,
preferably from 3000 to 50,000, more preferably from 3000 to
25,000.
[0017] Polymers useful in the overcoat compositions can be
homopolymers or can be copolymers having a plurality of distinct
repeat units, for example, two, three or four distinct repeat
units. The trimming compositions typically include a single
polymer, but can optionally include one or more additional polymer.
Suitable polymers and monomers for use in the overcoat compositions
are commercially available and/or can readily be made by persons
skilled in the art.
[0018] The trimming compositions further include one or more
aromatic acid that is free of fluorine. Fluorine-free aromatic
acids can be more environmentally friendly than fluorinated acids.
In the case of a photoresist based on deprotection reaction, the
acid with heat can cleave the bond of acid labile groups in the
photoresist pattern.
[0019] The aromatic acid is preferably a sulfonic acid comprising a
phenyl, biphenyl, naphthyl, anthracenyl, thiophene or furan group.
The aromatic acid is preferably chosen from one or more aromatic
sulfonic acids of the following general formulas (I)-(VI):
##STR00001##
wherein: R.sup.1 independently represents a substituted or
unsubstituted C1-C20 alkyl group, a substituted or unsubstituted
C5-C20 aryl group or a combination thereof, optionally containing
one or more group chosen from carbonyl, carbonyloxy, sulfonamido,
ether, thioether, a substituted or unsubstituted alkylene group, or
a combination thereof; Z.sup.1 independently represents a group
chosen from carboxyl, hydroxy, nitro, cyano, C1 to C5 alkoxy,
formyl and sulfonic acid; a and b are independently an integer from
0 to 5; and a+b is 5 or less;
##STR00002##
wherein: R.sup.2 and R.sup.3 each independently represents a
substituted or unsubstituted C1-C20 alkyl group, a substituted or
unsubstituted C5-C16 aryl group or a combination thereof,
optionally containing one or more group chosen from carbonyl,
carbonyloxy, sulfonamido, ether, thioether, a substituted or
unsubstituted alkylene group, or a combination thereof; Z.sup.2 and
Z.sup.3 each independently represents a group chosen from carboxyl,
hydroxy, nitro, cyano, C1 to C5 alkoxy, formyl and sulfonic acid; c
and d are independently an integer from 0 to 4; c+d is 4 or less; e
and f are independently an integer from 0 to 3; and e+f is 3 or
less;
##STR00003##
wherein: R.sup.4, R.sup.5 and R.sup.6 each independently represents
a substituted or unsubstituted C1-C20 alkyl group, a substituted or
unsubstituted C5-C12 aryl group or a combination thereof,
optionally containing one or more group chosen from carbonyl,
carbonyloxy, sulfonamido, ether, thioether, a substituted or
unsubstituted alkylene group, or a combination thereof; Z.sup.4,
Z.sup.5 and Z.sup.6 each independently represents a group chosen
from carboxyl, hydroxy, nitro, cyano, C1 to C5 alkoxy, formyl and
sulfonic acid; g and h are independently an integer from 0 to 4;
g+h is 4 or less; i and j are independently an integer from 0 to 2;
i+j is 2 or less; k and l are independently an integer from 0 to 3;
and k+l is 3 or less;
##STR00004##
wherein: R.sup.4, R.sup.5 and R.sup.6 each independently represents
a substituted or unsubstituted C1-C20 alkyl group, a substituted or
unsubstituted C5-C12 aryl group or a combination thereof,
optionally containing one or more group chosen from carbonyl,
carbonyloxy, sulfonamido, ether, thioether, a substituted or
unsubstituted alkylene group, or a combination thereof; Z.sup.4,
Z.sup.5 and Z.sup.6 each independently represents a group chosen
from carboxyl, hydroxy, nitro, cyano, C1 to C5 alkoxy, formyl and
sulfonic acid; g and h are independently an integer from 0 to 4;
g+h is 4 or less; i and j are independently an integer from 0 to 1;
i+j is 1 or less; k and l are independently an integer from 0 to 4;
and k+l is 4 or less;
##STR00005##
wherein: R.sup.7 and R.sup.8 each independently represents a
substituted or unsubstituted C1-C20 alkyl group, a substituted or
unsubstituted C5-C14 aryl group or a combination thereof,
optionally containing one or more group chosen from carboxyl,
carbonyl, carbonyloxy, sulfonamido, ether, thioether, a substituted
or unsubstituted alkylene group, or a combination thereof; Z.sup.7
and Z.sup.8 each independently represents a group chosen from
hydroxy, nitro, cyano, C1 to C5 alkoxy, formyl and sulfonic acid; m
and n are independently an integer from 0 to 5; m+n is 5 or less; o
and p are independently an integer from 0 to 4; and o+p is 4 or
less; and
##STR00006##
wherein: X is O or S; R.sup.9 independently represents a
substituted or unsubstituted C1-C20 alkyl group, a substituted or
unsubstituted C5-C20 aryl group or a combination thereof,
optionally containing one or more group chosen from carbonyl,
carbonyloxy, sulfonamido, ether, thioether, a substituted or
unsubstituted alkylene group, or a combination thereof; Z.sup.9
independently represents a group chosen from carboxyl, hydroxy,
nitro, cyano, C1 to C5 alkoxy, formyl and sulfonic acid; q and r
are independently an integer from 0 to 3; and q+r is 3 or less. For
each of the structures, it should be clear that the
R.sup.1--R.sup.9 groups can optionally form a fused structure
together with their respective associated rings. The aromatic acid
is typically present in the compositions in an amount of from 0.01
to 20 wt %, more typically from 0.1 to 10 wt % or from 1 to 5 wt %,
based on total solids of the trimming composition.
[0020] Exemplary aromatic acids for use in the pattern trimming
compositions include, without limitation, the following:
##STR00007## ##STR00008## ##STR00009## ##STR00010##
[0021] The trimming compositions further include a solvent or
solvent mixture. The trimming compositions can take the form of an
aqueous solution. Suitable solvent materials to formulate and cast
the trimming compositions exhibit very good solubility
characteristics with respect to the non-solvent components of the
trimming composition, but do not appreciably dissolve the
underlying photoresist pattern so as to minimize intermixing. The
solvent is typically chosen from water, organic solvents and
mixtures thereof. Suitable organic solvents for the trimming
composition include, for example: alkyl esters such as alkyl
propionates such as n-butyl propionate, n-pentyl propionate,
n-hexyl propionate and n-heptyl propionate, and alkyl butyrates
such as n-butyl butyrate, isobutyl butyrate and isobutyl
isobutyrate; ketones such as 2,5-dimethyl-4-hexanone and
2,6-dimethyl-4-heptanone; aliphatic hydrocarbons such as n-heptane,
n-nonane, n-octane, n-decane, 2-methylheptane, 3-methylheptane,
3,3-dimethylhexane and 2,3,4-trimethylpentane, and fluorinated
aliphatic hydrocarbons such as perfluoroheptane; alcohols such as
straight, branched or cyclic C.sub.4-C.sub.9 monohydric alcohol
such as 1-butanol, 2-butanol, isobutyl alcohol, tert-butyl alcohol,
3-methyl-1-butanol, 1-pentanol, 2-pentanol, 4-methyl-2-pentanol,
1-hexanol, 1-heptanol, 1-octanol, 2-hexanol, 2-heptanol, 2-octanol,
3-hexanol, 3-heptanol, 3-octanol and 4-octanol;
2,2,3,3,4,4-hexafluoro-1-butanol,
2,2,3,3,4,4,5,5-octafluoro-1-pentanol and
2,2,3,3,4,4,5,5,6,6-decafluoro-1-hexanol, and C.sub.5-C.sub.9
fluorinated diols such as 2,2,3,3,4,4-hexafluoro-1,5-pentanediol,
2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol and
2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-octanediol; ethers such as
isopentyl ether and dipropylene glycol monomethyl ether; and
mixtures containing one or more of these solvents. Of these organic
solvents, alcohols, aliphatic hydrocarbons and ethers are
preferred. The solvent component of the trimming composition is
typically present in an amount of from 90 to 99 wt % based on the
trimming composition.
[0022] The trimming compositions may include optional additives.
For example, the trimming compositions can include an additional
component that reacts with surface region of the resist pattern,
rendering the surface region soluble in an organic solvent rinsing
agent. This optional component preferably contains functional
groups chosen from --OH, --NH, --SH, ketones, aldehydes, --SiX
wherein X is a halogen, vinyl ethers and combinations thereof.
Without wishing to be bound by any particular theory, it is
believed that the component diffuses into the resist pattern and
reacts with carboxylic acid groups of the pattern. This reaction
results in a polarity change of the surface, rendering the surface
soluble in the organic solvent. This component can be useful, for
example, where the photoresist pattern is formed by negative tone
development (NTD) wherein the pattern is composed of unexposed
portions of the photoresist comprising acid-labile groups. Such
component if used is typically present in an amount of from 0.1 to
10 wt % based on total solids of the trimming composition.
[0023] The trimming composition can further include a surfactant.
Typical surfactants include those which exhibit an amphiphilic
nature, meaning that they can be both hydrophilic and hydrophobic
at the same time. Amphiphilic surfactants possess a hydrophilic
head group or groups, which have a strong affinity for water and a
long hydrophobic tail, which is organophilic and repels water.
Suitable surfactants can be ionic (i.e., anionic, cationic) or
nonionic. Further examples of surfactants include silicone
surfactants, poly(alkylene oxide) surfactants, and fluorochemical
surfactants. Suitable non-ionic surfactants include, but are not
limited to, octyl and nonyl phenol ethoxylates such as TRITON.RTM.
X-114, X-100, X-45, X-15 and branched secondary alcohol ethoxylates
such as TERGITOL.TM. TMN-6 (The Dow Chemical Company, Midland,
Mich. USA). Still further exemplary surfactants include alcohol
(primary and secondary) ethoxylates, amine ethoxylates, glucosides,
glucamine, polyethylene glycols, poly(ethylene glycol-co-propylene
glycol), or other surfactants disclosed in McCutcheon's Emulsifiers
and Detergents, North American Edition for the Year 2000 published
by Manufacturers Confectioners Publishing Co. of Glen Rock, N.J.
Nonionic surfactants that are acetylenic diol derivatives also can
be suitable. Such surfactants are commercially available from Air
Products and Chemicals, Inc. of Allentown, Pa. and sold under the
trade names of SURFYNOL.RTM. and DYNOL.RTM.. Additional suitable
surfactants include other polymeric compounds such as the tri-block
EO-PO-EO co-polymers PLURONIC.RTM. 25R2, L121, L123, L31, L81, L101
and P123 (BASF, Inc.). Such surfactant and other optional additives
if used are typically present in the composition in minor amounts
such as from 0.01 to 10 wt % based on total solids of the trimming
composition.
[0024] The trimming compositions are preferably free of
cross-linking agents as such materials can result in a dimensional
increase of the resist pattern.
[0025] The trimming compositions can be prepared following known
procedures. For example, the compositions can be prepared by
dissolving solid components of the composition in the solvent
components. The desired total solids content of the compositions
will depend on factors such as the desired final layer thickness.
Preferably, the solids content of the trimming compositions is from
1 to 10 wt %, more preferably from 1 to 5 wt %, based on the total
weight of the composition.
Photoresist Pattern Trimming Methods
[0026] Processes in accordance with the invention will now be
described with reference to FIG. 1A-I, which illustrates an
exemplary process flow for forming a photolithographic pattern
using a photoresist pattern trimming technique in accordance with
the invention. While the illustrated process flow is of a positive
tone development process, the invention is also applicable to
negative tone development (NTD) processes. Also, while the
illustrated process flow describes an LLE double patterning
process, it should be clear that the trimming method can be used in
any lithographic process where trimming of the photoresist pattern
would be beneficial, for example, in other double patterning
processes such as litho-etch-litho-etch (LELE) or self-aligned
double patterning (SADP), as an ion implantation mask, or simply
for patterning of one or more underlying layers.
[0027] FIG. 1A depicts in cross-section a substrate 100 which may
include various layers and features. The substrate can be of a
material such as a semiconductor, such as silicon or a compound
semiconductor (e.g., III-V or II-VI), glass, quartz, ceramic,
copper and the like. Typically, the substrate is a semiconductor
wafer, such as single crystal silicon or compound semiconductor
wafer, and may have one or more layers and patterned features
formed on a surface thereof. One or more layers to be patterned 102
may be provided over the substrate 100. Optionally, the underlying
base substrate material itself may be patterned, for example, when
it is desired to form trenches in the substrate material. In the
case of patterning the base substrate material itself, the pattern
shall be considered to be formed in a layer of the substrate.
[0028] The layers may include, for example, one or more conductive
layers such as layers of aluminum, copper, molybdenum, tantalum,
titanium, tungsten, alloys, nitrides or silicides of such metals,
doped amorphous silicon or doped polysilicon, one or more
dielectric layers such as layers of silicon oxide, silicon nitride,
silicon oxynitride, or metal oxides, semiconductor layers, such as
single-crystal silicon, and combinations thereof. The layers to be
etched can be formed by various techniques, for example, chemical
vapor deposition (CVD) such as plasma-enhanced CVD, low-pressure
CVD or epitaxial growth, physical vapor deposition (PVD) such as
sputtering or evaporation, or electroplating. The particular
thickness of the one or more layers to be etched 102 will vary
depending on the materials and particular devices being formed.
[0029] Depending on the particular layers to be etched, film
thicknesses and photolithographic materials and process to be used,
it may be desired to dispose over the layers 102 a hard mask layer
103 and/or a bottom antireflective coating (BARC) 104 over which a
first photoresist layer 106 is to be coated. Use of a hard mask
layer may be desired, for example, with very thin resist layers,
where the layers to be etched require a significant etching depth,
and/or where the particular etchant has poor resist selectivity.
Where a hard mask layer is used, the resist patterns to be formed
can be transferred to the hard mask layer 103 which, in turn, can
be used as a mask for etching the underlying layers 102. Suitable
hard mask materials and formation methods are known in the art.
Typical materials include, for example, tungsten, titanium,
titanium nitride, titanium oxide, zirconium oxide, aluminum oxide,
aluminum oxynitride, hafnium oxide, amorphous carbon, silicon
oxynitride and silicon nitride. The hard mask layer can include a
single layer or a plurality of layers of different materials. The
hard mask layer can be formed, for example, by chemical or physical
vapor deposition techniques.
[0030] A bottom antireflective coating may be desirable where the
substrate and/or underlying layers would otherwise reflect a
significant amount of incident radiation during photoresist
exposure such that the quality of the formed pattern would be
adversely affected. Such coatings can improve depth-of-focus,
exposure latitude, linewidth uniformity and CD control.
Antireflective coatings are typically used where the resist is
exposed to deep ultraviolet light (300 nm or less), for example,
KrF excimer laser light (248 nm) or ArF excimer laser light (193
nm). The antireflective coating can comprise a single layer or a
plurality of different layers. Suitable antireflective materials
and methods of formation are known in the art. Antireflective
materials are commercially available, for example, those sold under
the AR.TM. trademark by Rohm and Haas Electronic Materials LLC
(Marlborough, Mass. USA), such as AR.TM.40A and AR.TM.124
antireflectant materials.
[0031] A first photoresist layer 106 formed from a chemically
amplified photosensitive composition comprising a matrix polymer
having acid labile groups is disposed on the substrate over the
antireflective layer (if present). The photoresist composition can
be applied to the substrate by spin-coating, dipping,
roller-coating or other conventional coating technique. Of these,
spin-coating is typical. For spin-coating, the solids content of
the coating solution can be adjusted to provide a desired film
thickness based upon the specific coating equipment utilized, the
viscosity of the solution, the speed of the coating tool and the
amount of time allowed for spinning. A typical thickness for the
first photoresist layer 106 is from about 500 to 3000 .ANG..
[0032] The layer 106 can next be softbaked to minimize the solvent
content in the layer, thereby forming a tack-free coating and
improving adhesion of the layer to the substrate. The softbake can
be conducted on a hotplate or in an oven, with a hotplate being
typical. The softbake temperature and time will depend, for
example, on the particular material of the photoresist and
thickness. Typical softbakes are conducted at a temperature of from
about 90 to 150.degree. C., and a time of from about 30 to 90
seconds.
[0033] The first photoresist layer 106 is next exposed to
activating radiation 108 through a photomask 110 to create a
difference in solubility between exposed and unexposed regions.
References herein to exposing a photoresist composition to
radiation that is activating for the composition indicates that the
radiation is capable of forming a latent image in the photoresist
composition. The photomask has optically transparent and optically
opaque regions corresponding to regions of the resist layer to be
exposed and unexposed, respectively, by the activating radiation.
The exposure wavelength is typically sub-400 nm, sub-300 nm or
sub-200 nm such as 193 nm or EUV wavelengths (e.g., 13.5 nm), with
193 nm and EUV being preferred. The exposure energy is typically
from about 10 to 80 mJ/cm.sup.2, dependent upon the exposure tool
and the components of the photosensitive composition.
[0034] Following exposure of the first photoresist layer 106, a
post-exposure bake (PEB) is performed. The PEB can be conducted,
for example, on a hotplate or in an oven. Conditions for the PEB
will depend, for example, on the particular photoresist composition
and layer thickness. The PEB is typically conducted at a
temperature of from about 80 to 150.degree. C., and a time of from
about 30 to 90 seconds. A latent image defined by the boundary
between polarity-switched and unswitched regions (corresponding to
exposed and unexposed regions, respectively) is thereby formed.
[0035] The first photoresist layer 106 is next developed to remove
exposed regions of the layer, leaving unexposed regions forming a
first resist pattern 106' having a plurality of features as shown
in FIG. 1B. The features are not limited and can include, for
example, a plurality of lines and/or cylindrical posts which will
allow for the formation of line and/or contact hole patterns in the
underlying layers to be patterned. In the case of a negative tone
development process, where unexposed regions of the photoresist
layer are removed and exposed regions remain to form the first
pattern, an organic solvent developer is employed. The organic
developer can, for example, be a solvent chosen from ketones,
esters, ethers, hydrocarbons, and mixtures thereof, with
2-heptanone and n-butyl acetate being typical.
[0036] It is typical that the first resist pattern, for example,
the plurality of lines and/or posts have a duty ratio of 1:2 or
more, 1:1.5 or more or 1:1 or more before trimming. In the case of
lines and posts, duty ratio is defined as the ratio of linewidth or
post diameter (L) to the space length (S) between adjacent lines or
posts, respectively (i.e., L:S). A higher duty ratio refers to a
higher density of lines or posts, while a lower duty ratio refers
to a lower density of (i.e., more isolated) lines or posts. With
reference to FIG. 1B, the duty ratio prior to trimming is
L.sub.1:S.sub.1.
[0037] A layer 112 of a photoresist pattern trimming composition as
described herein is formed over the first photoresist pattern 106'
as shown in FIG. 1C. The trimming composition is typically applied
to the substrate by spin-coating. The solids content of the coating
solution can be adjusted to provide a desired film thickness based
upon the specific coating equipment utilized, the viscosity of the
solution, the speed of the coating tool and the amount of time
allowed for spinning. A typical thickness for the pattern trimming
layer 112 is from 200 to 1500 .ANG..
[0038] As shown in FIG. 1D, the substrate is next baked to remove
solvent in the trimming layer, to allow for the free acid to
diffuse into the surface of the underlying first resist pattern
106' and the polarity-changing reaction in the first resist pattern
surface region 114. The bake can be conducted with a hotplate or
oven 116, with a hotplate being typical. Suitable bake temperatures
are greater than 50.degree. C., for example, greater than
70.degree. C., greater than 90.degree. C., greater than 120.degree.
C. or greater than 150.degree. C., with a temperature of from 70 to
160.degree. C. and a time of from about 30 to 90 seconds being
typical. While a single baking step is typical, multiple-step
baking can be used and may be useful for resist profile
adjustment.
[0039] The first photoresist pattern is next contacted with a
rinsing agent, typically a developing solution, to remove the
residual trimming composition layer 112 and the surface region 114
of the first photoresist pattern 106'', with the resulting trimmed
pattern being shown in FIG. 1E. The rinsing agent is typically an
aqueous alkaline developer, for example, a quaternary ammonium
hydroxide solution, for example, a tetra-alkyl ammonium hydroxide
solutions such as 0.26 Normality (N) (2.38 wt %)
tetramethylammonium hydroxide (TMAH). Alternatively, an organic
solvent developer can be used, for example, a solvent chosen from
ketones, esters, ethers, hydrocarbons, and mixtures thereof, such
as 2-heptanone and n-butyl acetate. The rinsing agent can further
be or comprise water. As can be seen, the duty ratio of the first
resist pattern after trimming (L.sub.2:S.sub.2) is smaller prior to
trimming. The post-trimming duty ration can be, for example, 1:2 or
less, 1:3 or less or 1:4 or less. In the case of a double
patterning process, a typical duty ratio is about 1:1 before
trimming and about 1:3 after trimming.
[0040] The trimmed resist pattern can be used for patterning of
underlying layers at this point, as an ion implantation mask, or
another purpose. The following description pertains to an LLE
double patterning process. In LLE processes, the first resist
pattern is typically stabilized prior to formation of the second
resist pattern. Various resist stabilization techniques have been
proposed such as ion implantation, UV curing, thermal hardening,
thermal curing and chemical curing. Techniques are described, for
example, in US2008/0063985A1, US 2008/0199814A1 and US
2010/0330503A1.
[0041] A second photoresist composition is coated over the first
resist pattern 106'' and BARC layer 104 to form a second
photoresist layer 118, as shown in FIG. 1E. The second photoresist
composition can be the same as or different from the photoresist
composition used in forming the first resist layer and can be
applied and processed in the same manner including the materials
and conditions described above with respect to the first
photoresist layer. The second photoresist composition is preferably
positive-acting. Generally, selection for this composition will
depend on the particular application and geometries involved. In
the illustrated method, both the first and second photosensitive
compositions are positive acting.
[0042] The second photoresist layer 118 can next be softbaked. If
exposure of this layer is to be conducted with an immersion
lithography tool, an immersion topcoat layer (not shown) can be
disposed over the second photoresist layer. If a topcoat layer is
used, the second photoresist layer 118 can be softbaked after the
topcoat layer composition has been applied.
[0043] With reference to FIG. 1(F), the second photoresist layer
118 is selectively exposed to activating radiation 108 through a
second photomask 120 which has optically opaque regions
corresponding to portions of the second photoresist layer to remain
after development for a positive tone development method. The
exposed second photoresist layer 114 is heat-treated in a
post-exposure bake and developed, leaving behind second resist
pattern 118' disposed between lines of the first resist pattern
106'', as depicted in FIG. 1G.
[0044] Next, the BARC layer 104 is selectively etched using the
first and second resist patterns 106'', 118' simultaneously as an
etch mask, exposing the underlying hardmask layer 103. The hardmask
layer is next selectively etched, again using the first and second
resist patterns simultaneously as an etch mask, resulting in
patterned BARC and hardmask layers 104', 103', as shown in FIG. 1H.
Suitable etching techniques and chemistries for etching the BARC
layer and hardmask layer are known in the art and will depend, for
example, on the particular materials of these layers. Dry-etching
processes such as reactive ion etching are typical. The first and
second resist patterns 106'', 118' and patterned BARC layer 104'
are next removed from the substrate using known techniques, for
example, an oxygen plasma ashing. Using the hardmask pattern 103'
as an etch mask, the one or more layers 102 are then selectively
etched. Suitable etching techniques and chemistries for etching the
underlying layers 102 are known in the art, with dry-etching
processes such as reactive ion etching being typical. The patterned
hardmask layer 103' can next be removed from the substrate surface
using known techniques, for example, a dry-etching process such as
reactive ion etching. The resulting double patterned structure is a
pattern of etched features 102' as illustrated in FIG. H. In an
alternative exemplary method, it may be desirable to pattern the
layer 102 directly using the modified first photoresist pattern
106'' and second pattern 118' without the use of a hardmask layer
103. Whether direct patterning with the resist patterns can be
employed will depend on factors such as the materials involved,
resist selectivity, resist pattern thickness and pattern
dimensions.
[0045] The following non-limiting examples are illustrative of the
invention.
EXAMPLES
Photoresist Formulation and Resist Patterning
Example 1
[0046] The following monomers M1-M4 were used to form polymers for
the photoresist composition described below:
##STR00011##
A positive chemically amplified photoresist composition was
prepared by combining 1.28 g Polymer A (M1/M2/M3=4/4/2 mole ratio,
Mw=10K), 1.28 g Polymer B (M1/M2/M3/M4=30/35/15/20, Mw=7K), 0.56 g
of 4-(t-butylphenyl) tetramethylenesuflonium
4-(adamantane-1-carbonyloxy)-1,1,2,2-tetrafluorobutane sulfonate
(TMS-Ad-TFBS), 0.078 g Trihydroxymethyl-carbamic acid tert-butyl
ester, 0.003 g POLYFOX 656 surfactant, 33.56 g propylene glycol
methyl ether acetate and 63.25 g methyl-2-hydroxy-iso-butyrate.
[0047] Resist A was spin-coated on an organic bottom antireflective
coating (BARC AR.TM.124 23 nm/AR26N, 77 nm, Dow Electronic
Materials, Marlborough, Mass.) over 12 inch silicon wafers and
softbaked at 95.degree. C. for 60 sec. Then a 30 nm layer of
OC.TM.2000 topcoat (Dow Electronic Materials) was applied on the
resist. The coated wafer was exposed on an ASML ArF 1900i immersion
scanner with NA=1.30, Dipole 35Y illumination (0.9/0.635sigma),
plus x polarization, using a mask having line and space patterns,
and then post-exposure baked at 80.degree. C. for 60 sec. The
coated wafers were then treated with 0.26N (normal) aqueous
tetramethylammonium hydroxide (TMAH) solution to develop a 45 nm
1:1 line and space pattern imaged resist layer (i.e., duty
ratio=1:1).
Photoresist Trimming Compositions and Pattern Trimming
Example 2
PTC 1
[0048] 2.388 g copolymer of t-butyl acrylate/methacrylic acid (7/3
of mole ratio), 0.062 g p-toluenesulfonic acid, 19.51 g decane and
78.04 g 2-methyl-1-butynol were mixed until all components
dissolved and the mixture was filtered with a 0.2 micron Nylon
filter, resulting in a photoresist trimming composition (PTC 1). A
60 nm film of PTC 1 was spin-coated on a photoresist-coated wafer
of Example 1, baked at 70.degree. C. for 60 s on a hotplate and
developed in 2.38% TMAH developer for 12 s with a TEL Lithus GP
nozzle.
Example 3
PTC 2
[0049] 2.342 g copolymer of t-butyl acrylate/methacrylic acid (7/3
of mole ratio), 0.108 g p-toluenesulfonic acid, 19.51 g decane and
78.04 g 2-methyl-1-butynol were mixed until all components
dissolved and the mixture was filtered with a 0.2 micron Nylon
filter, resulting in a photoresist trimming composition PTC 2. A 60
nm film of PTC 2 was spin-coated on a photoresist-coated wafer of
Example 1, baked at 70.degree. C. for 60 s on a hotplate and
developed in 2.38% TMAH developer for 12 s with a TEL Lithus GP
nozzle.
Example 4
PTC 3
[0050] 2.363 g copolymer of t-butyl acrylate/methacrylic acid (7/3
of mole ratio), 0.087 g 2,4-dinitrobenzenesulfonic acid, 19.51 g
decane and 78.04 g 2-methyl-1-butynol were mixed until all
components dissolved and the mixture was filtered with a 0.2 micron
Nylon filter, resulting in a photoresist trimming composition PTC
3. A 60 nm film of PTC 3 was spin-coated on a photoresist-coated
wafer of Example 1, baked at 70.degree. C. for 60 s on a hotplate
and developed in 2.38% TMAH developer for 12 s with a TEL Lithus GP
nozzle.
Comparative Example 1
PTC 4
[0051] 2.4 g copolymer t-butyl acrylate/methacrylic acid (7/3 of
mole ratio), 0.1 g perfluorobutanesulfonic acid, 19.5 g decane and
78 g 2-methyl-1-butynol were mixed until all components dissolved
and the mixture was filtered with a 0.2 micron Nylon filter,
resulting in a photoresist trimming composition PTC 4. A 60 nm film
of PTC 4 was spin-coated on a photoresist-coated wafer of Example
1, baked at 70.degree. C. for 60 s on a hotplate and developed in
2.38% TMAH developer for 12 s with a TEL Lithus GP nozzle.
Comparative Example 2
PTC 5
[0052] 2.374 g copolymer of t-butyl acrylate/methacrylic acid (7/3
of mole ratio), 0.076 g camphorsulfonic acid, 19.51 g decane and
78.04 g 2-methyl-1-butynol were mixed until all components
dissolved and the mixture was filtered with a 0.2 micron Nylon
filter, resulting in a photoresist trimming composition PTC 5. A 60
nm film of PTC 5 was spin-coated on a photoresist-coated wafer of
Example 1, baked at 70.degree. C. for 60 s on a hotplate and
developed in 2.38% TMAH developer for 12 s with a TEL Lithus GP
nozzle.
[0053] The results are shown below in Table 1.
TABLE-US-00001 TABLE 1 Final CD .DELTA.CD Example Acid/loading (nm)
(nm) 1 (no trimming) NA 45.2 NA 2 (PTC 1) PTSA (equimolar 31.4
-13.8 to PFBuS) 3 (PTC 2) PTSA (1.74x equimolar 25.1 -20.1 to
PFBuS) 4 (PTC 3) 2,4DBSA (equimolar 28 -17.2 to PFBuS) Comp. 1
(PTC4) PFBuS 25.2 -20 Comp. 2 (PTC 5) CSA (equimolar 41.1 -4.1 to
PFBuS) PTSA = p-toluenesulfonic acid; PFBuS =
perfluorobutanesulfonic acid; 2,4DBSA = 2,4-dinitrobenzenesulfonic
acid; CSA = camphorsulfonic acid
[0054] As can be seen, all acids were loaded in equimolar amounts
except for PTC 3 in Example 4, in which 2,4-dinitrobenzenesulfonic
acid was loaded in excess to match the shrink of PTC 4 (control) in
Comparative Example 1 containing perfluorobutanesulfonic acid
superacid. As can be seen, resist pattern trimming compositions PTC
1 and PTC 3 containing p-toluenesulfonic acid and
2,4-dinitrobenzenesulfonic acid, respectively, at equimolar loading
in Examples 2 and 4 in accordance with the invention resulted in
significant pattern trimming, although less than the
perfluorobutanesulfonic superacid of Comparative Example 1, and
significantly greater than the camphorsulfonic acid of Comparative
Example 2.
[0055] Matching of CD and CD change (ACD) in Example 3 and
Comparative Example 1 was done to allow for more accurate
comparison of linewidth roughness (LWR) and resist profile of the
resulting patterns. The wafers for these examples were visually
observed top-down by SEM. The same LWR (2.9 nm) and excellent
resist profiles were observed for both examples.
[0056] Advantages of resist trimming methods of the invention such
as those exemplified in Examples 2 and 3 over the use of a
superacid such as in Comparative Example 1 include, for example,
the lower price and lower volatility of the organic acids, which
makes it easier to manipulate these material in a manufacturing
environment.
* * * * *